Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) will be part of ESA's Sentinel-5 Precursor (S5P) satellite platform scheduled for launch in 2015. TROPOMI will monitor methane and carbon monoxide concentrations in the Earth's atmosphere by measuring spectra of back-scattered sunlight in the short-wave infrared (SWIR).

S5P will be the first satellite mission to rely uniquely on the spectral window at 4190–4340 cm⁻¹ (2.3 μm) to retrieve CH₄ and CO. In this study, we investigated if the absorption features of the three relevant molecules CH₄, CO, and H₂O are adequately known. To this end, we retrieved total columns of CH₄, CO, and H₂O from absorption spectra measured by two ground-based Fourier transform spectrometers that are part of the Total Carbon Column Observing Network (TCCON). The retrieval results from the 4190–4340 cm⁻¹ range at the TROPOMI resolution (0.45 cm⁻¹) were then compared to the CH₄ results obtained from the 6000 cm⁻¹ region, and the CO results obtained from the 4190–4340 cm⁻¹ region at the higher TCCON resolution (0.02 cm⁻¹).

For TROPOMI-like settings, we were able to reproduce the CH₄ columns to an accuracy of 0.3% apart from a constant bias of 1%. The CO retrieval accuracy was, through interference, systematically influenced by the shortcomings of the CH₄ and H₂O spectroscopy. In contrast to CH₄, the CO column error also varied significantly with atmospheric H₂O content. Unaddressed, this would introduce seasonal and latitudinal biases to the CO columns retrieved from TROPOMI measurements. We therefore recommend further effort from the spectroscopic community to be directed at the H₂O and CH₄ spectroscopy in the 4190–4340 cm⁻¹ region.